Motorator Experts - How to determine the right size cylinder heads to use?

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How to determine the right size cylinder heads to use?

Is there a way to determine how large your cylinder heads should be... Assuming a domestic V8, such as a small block Chevy or Ford. What intake port size should I choose? Is there a flow (cfm) number I should target given a certain HP goal? What about if the motor is supercharged vs. naturally aspirated?

Asked by: Goose

User type: Enthusiast

Asked on: March 19, 2009 21:42

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Answers

Dart Machinery
User type: Manufacturer
Posted: about 1 year ago

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A good rule of thumb is to base the port volume, on the projected power output. However let me caution you that that if you rate your engine's final output too optimistically you will end up with a port that is too big and the target output will not be reached. It's better to be a little too small than too big generally, and flow numbers shouldn't come into play, as they truthfully have a very small impact.

Here are some rough ranges for 23 degree SBC heads and 20 degree Ford heads:
Projected horsepower / Intake Port size
350-400 / 140-160
400-450 / 160-180
500-550 / 200-220
550-600 / 220-230
600-700 / 230+

Hope this helps!

Dart Machinery
User type: Manufacturer
Posted: about 1 year ago

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For reference, the chart is available in the questions section on our site here:

http://www.dartheads.com/customer_service_view.php?qk=34

Goose
User type: Enthusiast
Posted: about 1 year ago

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Awesome, thanks for the help!

TheRipper
User type: Enthusiast
Posted: about 1 year ago

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Those numbers are pretty close. I have heads for a SBF (Old Canfileds, and Edelbrock Victors) The Canfield flowed in the 230 Range and made 575hp on a 347 and the Victors made 620 on a 348 (no flow numbers just "small port"). Same cam carbs, mainfolds, both on Dart 8.2 Aluminum blocks (NICE). Link below is random mock up of the 575hp Dart Block mock up with injectors, but didn't get to run the stacks, just a damBest 4bbl carb.

References

http://www.gtsparkplugs.com/TigerEngine.html